You need to include self-contained testcase (this is not one) and write
what exact command line you used (KCC is some Japanesse package, did you mean
kgcc? What do you mean by using gcc as backend?).
I've added
#include <complex>
void checkVal(float,float);
at the start of the file and it compiled just fine with various optimization options,
with gcc, g++, egcs++, kgcc.